Bulk acoustic wave resonator filters with integrated capacitors

ABSTRACT

A device includes a piezoelectric layer on a substrate and including a portion included in an acoustic resonator, a first conductive layer on the piezoelectric layer and including a first electrode of the acoustic resonator on a first side of resonator portion of the piezoelectric layer, and a second conductive layer on the piezoelectric layer and including a second electrode of the acoustic resonator on a second side of the resonator portion of the piezoelectric layer. An insulating layer is disposed on the second conductive layer and an interconnection metal layer is electrically connected to the second conductive layer or the first conductive layer and has a portion extending onto the insulating layer and overlapping a portion of the second conductive layer to provide a capacitor electrode of a capacitor coupled to the first electrode and/or the second electrode.

BACKGROUND

The present invention relates generally to electronic devices andmethods of fabrication the same and, more particularly, bulk acousticwave (BAW) resonator devices and methods of fabricating the same.

Mobile telecommunication devices have been successfully deployedworld-wide. With the ramp of 4G/LTE in about 2012 and recent rollout of5G, and explosion of mobile data traffic, data rich content is drivingthe growth of the smartphone segment—which is expected to reach 2B perannum within the next few years. Coexistence of new and legacy standardsand thirst for higher data rate requirements is driving RF complexity insmartphones. Unfortunately, limitations of conventional RF technologycan be an impediment to development of devices to provide servicesaccording to these new standards. For example, 5G standards demands highperformance RF filters with frequencies around 5 GHz and higher. Filtersusing bulk acoustic wave resonators (BAWR) are leading candidates formeeting such demands.

SUMMARY

Some embodiments according to the invention provide a device including apiezoelectric layer on a substrate and including a portion included inan acoustic resonator, a first conductive layer on the piezoelectriclayer and including a first electrode of the acoustic resonator on afirst side of resonator portion of the piezoelectric layer, and a secondconductive layer on the piezoelectric layer and including a secondelectrode of the acoustic resonator on a second side of the resonatorportion of the piezoelectric layer. An insulating layer is disposed onthe second conductive layer and an interconnection metal layer iselectrically connected to the second conductive layer or the firstconductive layer and has a portion extending onto the insulating layerand overlapping a portion of the second conductive layer to provide acapacitor electrode of a capacitor coupled to the first electrode and/orthe second electrode.

In some embodiments, the device includes a conductive via thatelectrically connects the interconnection metal layer to the firstelectrode or the second electrode and the portion of the interconnectionmetal layer extends onto the insulation layer adjacent a location wherethe interconnection layer is disposed on and contacts the conductivevia. The conductive via may pass through the insulation layer and thepiezoelectric layer to contact the first electrode. The capacitorelectrode may overlap a portion of the second electrode.

In some embodiments, the conductive via may extend into and contact afirst portion of the second conductive layer that is electricallyisolated from a second portion of the second conductive layer that iselectrically connected to the first electrode. The capacitor electrodemay overlap the second portion of the second conductive layer.

In further embodiments, the piezoelectric layer may include a firstportion included in a first acoustic resonator and a second portionincluded in a second acoustic resonator. The first electrode may overlapthe first and second portions of the piezoelectric layer and the secondelectrode may include an electrode overlapping the first portion of thepiezoelectric layer and an electrode overlapping the second portion ofthe piezoelectric layer and the capacitor electrode. The capacitor maybe coupled between an input of the first acoustic resonator and anoutput of the second acoustic resonator.

In some embodiments, the acoustic resonator may include a first acousticresonator and a second acoustic resonator coupled in series. Thecapacitor electrode may include a capacitor electrode of a capacitorcoupled across the series combination of the first acoustic resonatorand the second acoustic resonator.

Further embodiments provide a device including an acoustic resonatorincluding a first electrode, a second electrode and a piezoelectricregion between the first and second electrodes and an insulating layeron the second electrode. The device further includes an interconnectionmetal layer on the acoustic resonator, connected by a via to the firstelectrode or the second electrode and having a portion extending ontothe insulation layer adjacent the via that serves as a capacitorelectrode.

The first electrode may be formed from a first conductive layer. Thesecond electrode may be formed from second conductive layer. The via mayconnect the interconnection metal layer to the first conductive layerand the capacitor electrode may overlap a portion of the secondconductive layer. The first electrode may be formed from a firstconductive layer and the second electrode may be formed from secondconductive layer. The via may connect the interconnection metal layer toa portion of the second conductive layer electrically connected to thefirst electrode and the capacitor electrode may overlap the portion ofthe second conductive layer electrically connected to the firstelectrode. The piezoelectric region may be formed from a piezoelectriclayer and the via may pass through the piezoelectric layer.

According to additional aspects, methods may include forming apiezoelectric layer on a substrate, forming a first conductive layer ona first side of the piezoelectric layer, patterning the first conductivelayer to form a first electrode for an acoustic resonator, and forming asecond conductive layer on a second side of the piezoelectric layer. Themethods further include patterning the second conductive layer to form asecond electrode of the acoustic resonator, forming an insulating layeron the second conductive layer, and forming an interconnection metallayer electrically connected to the second electrode layer or the firstelectrode layer and having a portion extending onto the insulating layerand overlapping a portion of the second conductive layer to provide acapacitor electrode of a capacitor coupled to the first electrode and/orthe second electrode.

Forming the interconnection metal layer may be preceded by forming aconductive via electrically connected to the first electrode or thesecond electrode. Forming the interconnection metal layer may includeforming the interconnection layer on the conductive via, wherein theportion of the interconnection metal layer extends onto the insulationlayer adjacent a location where the interconnection layer contacts theconductive via. Forming the conductive via may include forming aconductive via that passes through the insulation layer and thepiezoelectric layer to contact the first electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more fully understand embodiments of the present invention,reference is made to the accompanying drawings. Understanding that thesedrawings are not to be considered limitations in the scope of theinvention, the presently described embodiments and the presentlyunderstood best mode of the invention are described with additionaldetail through use of the accompanying drawings in which:

FIG. 1 is simplified cross-sectional view of an acoustic resonatordevice according to some embodiments.

FIG. 2 is a schematic illustration of a circuit implemented by thedevice of FIG. 1.

FIG. 3 is simplified cross-sectional view of an acoustic resonatordevice according to some embodiments.

FIG. 4 is a schematic illustration of a circuit implemented by thedevice of FIG. 3.

FIG. 5 is simplified cross-sectional view of an acoustic resonatordevice according to some embodiments.

FIG. 6 is a simplified plan view of the device of FIG. 5

FIG. 7 is a schematic illustration of a circuit implemented by thedevice of FIG. 5.

FIG. 8 is simplified cross-sectional view of an acoustic resonatordevice according to some embodiments.

FIG. 9 is a simplified plan view of the device of FIG. 8

FIG. 10 is a schematic illustration of a circuit implemented by thedevice of FIG. 8.

FIGS. 11-14 are cross-sectional views illustrating operations forfabricating the device of FIG. 1 according to some embodiments.

FIGS. 15-18 are cross-sectional views illustrating operations forfabricating the device of FIG. 3 according to some embodiments.

FIGS. 19-22 are cross-sectional views illustrating operations forfabricating the device of FIG. 5 according to some embodiments.

FIGS. 23-26 are cross-sectional views illustrating operations forfabricating the device of FIG. 8 according to some embodiments.

FIGS. 27 and 28 are graphs of simulated performance of a BAW resonatorfilter device with integrated capacitors according to some embodiments.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

According to the present invention, techniques generally related toelectronic devices are provided. More particularly, the presentinvention provides techniques related to BAW devices and methods offabricating the same. Merely by way of example, the invention has beenapplied to a single crystal resonator device for a communication device,mobile device, computing device, among others.

As used herein, the term “substrate” can mean the bulk substrate or caninclude overlying growth structures such as an aluminum, gallium, orternary compound of aluminum and gallium and nitrogen containingepitaxial region, or functional regions, combinations, and the like.

Devices according to some embodiments can be manufactured in arelatively simple and cost-effective manner while using conventionalmaterials and/or methods according to one of ordinary skill in the art.Such filters or resonators can be implemented in an RF filter device, anRF filter system, or the like. Depending upon the embodiment, one ormore of these benefits may be achieved. Of course, there can be othervariations, modifications, and alternatives.

With 4G LTE and 5G growing more popular by the day, wireless datacommunication demands high performance RF filters with frequenciesaround 5 GHz and higher. Bulk acoustic wave (BAW) resonators are leadingcandidates for such applications. BAW resonators typically include apiezoelectric material, e.g., aluminum nitride (AlN), in crystallineform, typically disposed between two electrodes, which commonly includemolybdenum (Mo), tungsten (W), or ruthenium (Ru).

Some embodiments of the inventive subject matter use interconnection andinsulation layers formed in fabricating BAW resonator-based filters toform capacitors that can be used to improve frequency responsecharacteristics of the filters. Such devices and methods can implementthese capacitor structures without major modification of existingtechniques for fabrication of the BAW resonators.

FIG. 1 illustrates a BAW filter device according to some embodiments.The device includes an acoustic resonator 170 formed in and/or on asubstrate 100. A first conductive layer 110 (e.g., a molybdenum (Mo)layer, a ruthenium (Ru) layer, a tungsten (W) layer, or the like) isdisposed on the substrate 100. The substrate 100 may include, forexample, one or more layers, such as silicon (Si) layers, silicon oxide(SiOx) layers, silicon carbide (SiC) layers, or the like. Apiezoelectric layer 120 (e.g., an aluminum nitride (AlN) layer, agallium nitride (GaN) layer, or the like) is disposed on the firstconductive layer 110. A second conductive layer 130 (e.g., a molybdenum(Mo) layer, a ruthenium (Ru) layer, a tungsten (W) layer, or the like)is disposed on the piezoelectric layer 120. A lower electrode 110 a ofthe resonator 170 is formed from the first conductive layer 110 and anupper electrode 130 a of the resonator 170 is formed from the secondconductive layer 130, on opposite sides of a portion 120 a of thepiezoelectric layer 120. An insulation layer 160 (e.g., a siliconnitride (SiN) layer, a silicon oxide (SiOx) layer or the like) isdisposed on the second conductive layer 130. An interconnection (IC)metal layer 150 (e.g., a layer comprising gold (Au), aluminum (Al),copper (Cu), nickel (Ni), aluminum bronze (AlCu), or other likematerials) is disposed on the insulation layer 160.

An electrode for a capacitor 180 electrically coupled between the bottomelectrode 110 a and the top electrode 130 a comprises an extension 150 aof the IC metal layer 150 adjacent a via including a portion 130 c ofthe second conductive layer 130 and a portion 150 b of the IC metallayer 150. The capacitor electrode provided by the IC metal layerextension 150 a overlaps a portion 130 b of the first conductive layer130, which serves as second capacitor electrode. The capacitordielectric is provided by a portion 160 a of the insulation layer 160between the IC metal layer extension 150 a and the underlying portion130 b of the second conductive layer 130. FIG. 2 is a simplifiedschematic diagram illustrating the electrical interconnections of theresonator 170 and the capacitor 180, showing that the capacitor 180 isconnected between input and output terminals of the resonator 170.

FIG. 3 illustrates a BAW filter device according to further embodiments.The device includes an acoustic resonator 370 disposed in and/or on asubstrate 300. A first conductive layer 310 (e.g., a molybdenum (Mo)layer, a ruthenium (Ru) layer, a tungsten (W) layer, or the like) isdisposed on the substrate 300. A piezoelectric material layer 320 (e.g.,an aluminum nitride (AlN) layer, a gallium nitride (GaN) layer, or thelike) is disposed on the first conductive layer 310. A second conductivelayer 330 (e.g., a molybdenum (Mo) layer, a ruthenium (Ru) layer, atungsten (W) layer, or the like) is disposed on the piezoelectric layer320. A lower electrode 310 a of the resonator 370 is formed from thefirst conductive layer 310 and an upper electrode 330 a of the resonator370 is formed from the second conductive layer 330, on opposite sides ofa portion 320 a of the piezoelectric layer 320, thus forming theresonator 370.

An insulation layer 360 (e.g., a silicon nitride (SiN) layer, a siliconoxide (SiOx) layer or the like) is disposed on the second conductivelayer 330. An interconnection (IC) metal layer 350 (e.g., a layercomprising gold (Au), aluminum (Al), copper (Cu), nickel (Ni), aluminumbronze (AlCu), or other like materials) is disposed on the insulationlayer 360. As shown, an electrode of a capacitor 380 electricallycoupled between the bottom electrode 310 a and the top electrode 330 ais formed from an extension 350 a of the IC metal layer 350 adjacent avia including a portion 330 c of the second conductive layer 330 and aportion 350 b of the IC metal layer 350. The capacitor electrodeprovided by the extension 350 a overlies a portion 330 b of the firstconductive layer 330, which serves as second capacitor electrode. Thecapacitor dielectric is provided by a portion 360 a of the insulationlayer 360 between the IC metal layer extension 350 a and the underlyingportion 330 b of the second conductive layer 330. FIG. 4 is a simplifiedschematic diagram illustrating the electrical interconnections of theresonator 370 and the capacitor 380, showing that the capacitor 380 isconnected between input and output terminals of the resonator 370.

FIGS. 5-7 illustrate a BAW filter device according to some embodiments.The device includes an acoustic resonator 570 disposed on a substrate500. A first conductive layer 510 (e.g., a molybdenum (Mo) layer, aruthenium (Ru) layer, a tungsten (W) layer, or the like) is disposed onthe substrate 500. A piezoelectric material layer 520 (e.g., an aluminumnitride (AlN) layer, a gallium nitride (GaN) layer, or the like) isdisposed on the first conductive layer 510. A second conductive layer530 (e.g., a molybdenum (Mo) layer, a ruthenium (Ru) layer, a tungsten(W) layer, or the like) is disposed on the piezoelectric layer 520. Alower electrode 510 a of the resonator 570 is formed from the firstconductive layer 510 and an upper electrode 530 a of the resonator 570is formed from the second conductive layer 530, on opposite sides of aportion 520 a of the piezoelectric layer 520.

An insulation layer 560 (e.g., a silicon nitride (SiN) layer, a siliconoxide (SiOx) layer or the like) is disposed on the second conductivelayer 530. An interconnection (IC) metal layer 550 (e.g., a layercomprising gold (Au), aluminum (Al), copper (Cu), nickel (Ni), aluminumbronze (AlCu), or other like materials) is disposed on the insulationlayer 560. As shown, an electrode of a capacitor 580 electricallycoupled between the bottom electrode 510 a and the top electrode 530 ais formed from an extension 550 a of the IC metal layer 550 adjacent avia including a portion 550 c of the IC metal layer 550. The capacitorelectrode provided by the extension 550 a overlies a portion 530 b ofthe first conductive layer 530, which serves as second capacitorelectrode. The capacitor dielectric is provided by a portion 560 a ofthe insulation layer 560 between the IC metal layer extension 550 a andthe underlying portion 530 b of the second conductive layer 530. FIG. 7is a simplified schematic diagram illustrating the electricalinterconnections of the resonator 570 and the capacitor 580, showingthat the capacitor 580 is connected between input and output terminalsof the resonator 570.

FIGS. 8-10 illustrate a BAW filter device according to furtherembodiments. The device includes first and second acoustic resonators870 a, 870 b disposed on a substrate 800. A first conductive layer 810(e.g., a molybdenum (Mo) layer, a ruthenium (Ru) layer, a tungsten (W)layer, or the like) is disposed on the substrate 800. A piezoelectricmaterial layer 820 (e.g., an aluminum nitride (AlN) layer, a galliumnitride (GaN) layer, or the like) is disposed on the first conductivelayer 810. A second conductive layer 830 (e.g., a molybdenum (Mo) layer,a ruthenium (Ru) layer, a tungsten (W) layer, or the like) is disposedon the piezoelectric layer 820. A lower electrode 810 a of the firstresonator 870 a is formed from the first conductive layer 810 and anupper electrode 830 a of the first resonator 870 a is formed from thesecond conductive layer 830, on opposite sides of a portion 820 a of thepiezoelectric layer 820. A lower electrode 810 b of the second resonator870 b is formed from the first conductive layer 810 and an upperelectrode 830 b of the second resonator 870 b is formed from the secondconductive layer 830, on opposite sides of a portion 820 b of thepiezoelectric layer 820.

An insulation layer 860 (e.g., a silicon nitride (SiN) layer, a siliconoxide (SiOx) layer or the like) is disposed on the second conductivelayer 830. An interconnection (IC) metal layer 850 (e.g., a layercomprising gold (Au), aluminum (Al), copper (Cu), nickel (Ni), aluminumbronze (AlCu), or other like materials) is disposed on the insulationlayer 860. As shown, an electrode of a capacitor 880 electricallycoupled between the bottom electrode 810 a and the top electrode 830 ais formed from an extension 850 a of the IC metal layer 850 adjacent avia including a portion 850 b of the IC metal layer 850. The capacitorelectrode provided by the extension 850 a overlies a portion 830 c ofthe first conductive layer 830, which serves as second capacitorelectrode. The capacitor dielectric is provided by a portion 860 a ofthe insulation layer 860 between the IC metal layer extension 850 a andthe underlying portion 830 c of the second conductive layer 830. FIG. 10is a simplified schematic diagram illustrating the electricalinterconnections of the first and second resonators 870 a, 870 b and thecapacitor 880, showing that the capacitor 880 is connected between inputterminal of the first resonator 870 a and the output terminal of thesecond resonator 870 b.

FIGS. 11-14 illustrate operations for fabricating the device of FIG. 1according to some embodiments. Referring to FIG. 11, a first conductivelayer 110 and a piezoelectric layer 120 are formed in a substrate 100,with at least a portion of the first conductive layer 510 overlying asacrificial layer 192. The first conductive layer 110 may be formed bydeposition of molybdenum (Mo), ruthenium (Ru), tungsten (W) layer, orthe like. The piezoelectric material layer 120 may be formed bydeposition of aluminum nitride (AlN), gallium nitride (GaN), or thelike. The sacrificial layer 192 can comprise, for example,polycrystalline silicon, amorphous silicon, silicon oxide (SiOx), or thelike. The structure illustrated in FIG. 11 can be fabricated, forexample, using operations of a transfer process along the lines ofprocesses described in U.S. Pat. No. 10,355,659 to Kim et al., thedisclosure of which is incorporated herein by reference in its entirety.

Referring to FIG. 12, a portion of the piezoelectric layer 120 isremoved to expose a portion of the first conductive layer 110, and asecond conductive layer 130 is formed on the piezoelectric layer 120.The second conductive layer 130 forms a via 130 c contacting the exposedportion of the first conductive layer 510. The second conductive layer130 may be formed, for example, by deposition of molybdenum (Mo),ruthenium (Ru), tungsten (W), or the like. Referring to FIG. 13, thesecond conductive layer 130 is patterned and then an insulation layer160 (e.g., a silicon nitride (SiN) layer, silicon oxide (SiOx) layer, orthe like) is formed on the patterned second conductive layer 130.Referring to FIG. 14, the insulation layer 160 is patterned, includingexposing portions of the second conductive layer 130, followed byforming an IC metal layer 150 (e.g., a layer comprising gold (Au),aluminum (Al), copper (Cu), nickel (Ni), aluminum bronze (AlCu), orother like materials) and removing the sacrificial layer 192 to form anair pocket 190.

FIGS. 15-18 illustrate operations for fabricating the device of FIG. 3according to some embodiments. Referring to FIG. 15, a first conductivelayer 310 and a piezoelectric layer 320 are formed in a substrate 300,with at least a portion of the first conductive layer 310 overlying asacrificial layer 392. The first conductive layer 310 may be formed bydeposition of molybdenum (Mo), ruthenium (Ru), tungsten (W) layer, orthe like. The piezoelectric material layer 320 may be formed bydeposition of aluminum nitride (AlN), gallium nitride (GaN), or thelike. The sacrificial layer 392 can comprise, for example,polycrystalline silicon, amorphous silicon, silicon oxide (SiOx), or thelike. The structure illustrated in FIG. 15 can be fabricated, forexample, using operations of a transfer process along the lines ofprocesses described in the aforementioned U.S. Pat. No. 10,355,659 toKim et al.

Referring to FIG. 16, a portion of the piezoelectric layer 320 isremoved to expose a portion of the first conductive layer 310, and asecond conductive layer 330 is formed on the piezoelectric layer 320.The second conductive layer 330 forms a via 330 b contacting the exposedportion of the first conductive layer 310. The second conductive layer330 may be formed, for example, by deposition of molybdenum (Mo),ruthenium (Ru), tungsten (W), or the like. Referring to FIG. 17, thesecond conductive layer 330 is patterned and then an insulation layer360 is formed on the patterned second conductive layer 330. Referring toFIG. 18, the insulation layer 360 is patterned, including exposingportions of the second conductive layer 330, followed by forming an ICmetal layer 350 (e.g., a layer comprising gold (Au), aluminum (Al),copper (Cu), nickel (Ni), aluminum bronze (AlCu), or other likematerials) and removing the sacrificial layer 192 to form an air pocket190.

FIGS. 19-22 illustrate operations for fabricating the device of FIG. 5according to some embodiments. Referring to FIG. 19, a first conductivelayer 510 and a piezoelectric layer 520 are formed in a substrate 500,with at least a portion of the first conductive layer 510 overlying asacrificial layer 592. The first conductive layer may be formed bydeposition of molybdenum (Mo), ruthenium (Ru), tungsten (W) layer, orthe like. The piezoelectric material layer 520 may be formed bydeposition of aluminum nitride (AlN), gallium nitride (GaN), or thelike. The sacrificial layer 592 can comprise, for example,polycrystalline silicon, amorphous silicon, silicon oxide (SiOx), or thelike. The structure illustrated in FIG. 11 can be fabricated, forexample, using operations of a transfer process along the lines ofprocesses described in the aforementioned U.S. Pat. No. 10,355,659 toKim et al.

Referring to FIG. 20, a portion of the piezoelectric layer 520 isremoved to expose a portion of the first conductive layer 510, and asecond conductive layer 530 is formed on the piezoelectric layer 520.The second conductive layer 530 forms a via 530 c contacting the exposedportion of the first conductive layer 510. The second conductive layer530 may be formed, for example, by deposition of molybdenum (Mo),ruthenium (Ru), tungsten (W), or the like. Referring to FIG. 21, thesecond conductive layer 530 is patterned and then an insulation layer560 is formed on the patterned second conductive layer 530. Referring toFIG. 22, the insulation layer 560 is patterned, including exposingportions of the second conductive layer 530, followed by forming an ICmetal layer 550 (e.g., a layer comprising gold (Au), aluminum (Al),copper (Cu), nickel (Ni), aluminum bronze (AlCu), or other likematerials) and removing the sacrificial layer 592 to form an air pocketunder the resonator 570.

FIGS. 23-26 illustrates operations for fabricating the device of FIG. 8according to some embodiments. Referring to FIG. 23, a substrate 800 isformed including a first conductive layer 810 and a piezoelectric layer820, with at least a portion of the first conductive layer 810 overlyinga sacrificial layer 892. The first conductive layer may be formed bydeposition of molybdenum (Mo), ruthenium (Ru), tungsten (W) layer, orthe like. The piezoelectric material layer 820 may be formed bydeposition of aluminum nitride (AlN), gallium nitride (GaN), or thelike. The sacrificial layer 892 may be formed from, for example,polycrystalline silicon, amorphous silicon, silicon oxide, or the like.The structure illustrated in FIG. 23 can be fabricated, for example,using operations of a transfer process along the lines of processesdescribed in the aforementioned U.S. Pat. No. 10,355,659 to Kim et al.

Referring to FIG. 24, a second conductive layer 830 is formed on thepiezoelectric layer 820. The second conductive layer 830 may be formed,for example, by deposition of molybdenum (Mo), ruthenium (Ru), tungsten(W), or the like. Referring to FIG. 25, the second conductive layer 830is patterned to expose portions of the piezoelectric layer 820. Aninsulation layer 860 is then formed on the patterned second conductivelayer 830. Referring to FIG. 26, the insulation layer 860 is patterned,including exposing portions of the second conductive layer 830, followedby forming and patterning an IC metal layer 850 (e.g., a layercomprising gold (Au), aluminum (Al), copper (Cu), nickel (Ni), aluminumbronze (AlCu), or other like materials) and removing the sacrificiallayer 892 to form an air pocket 890 underlying first and secondresonators 870 a, 870 b.

FIGS. 27 and 28 illustrate a simulated frequency response and Q,respectively, of a BAW resonator filter incorporating an integratedcapacitor along the lines described above. The capacitor may have anarea in a range of 100 Å to 20,000 Å and a capacitance in a range fromabout 0.05 pf to about 5 pf. The addition of the capacitor can increasethe sharpness of the upper passband skirt without appreciably affectingQ of the filter in comparison with a device lacking such a capacitor.Such on-chip capacitors can also be used to improve other filterperformance parameters, such as rejection, matching and harmonicrejection. The capacitor can improve nearby rejection withoutsubstantially increasing injection loss. A standalone resonator withoutsuch a capacitor may require a Q of 2500-3500 to provide similarperformance.

While the above is a full description of the specific embodiments,various modifications, alternative constructions and equivalents may beused. As an example, the packaged device can include any combination ofelements described above, as well as outside of the presentspecification. Therefore, the above description and illustrations shouldnot be taken as limiting the scope of the present invention which isdefined by the appended claims.

What is claimed:
 1. A device comprising: a piezoelectric layer on asubstrate and comprising a portion included in an acoustic resonator; afirst conductive layer on the piezoelectric layer and comprising a firstelectrode of the acoustic resonator on a first side of resonator portionof the piezoelectric layer; a second conductive layer on thepiezoelectric layer and comprising a second electrode of the acousticresonator on a second side of the resonator portion of the piezoelectriclayer; an insulating layer on the second conductive layer; and aninterconnection metal layer electrically connected to the secondconductive layer or the first conductive layer and having a portionextending onto the insulating layer and overlapping a portion of thesecond conductive layer to provide a capacitor electrode of a capacitorcoupled to the first electrode and/or the second electrode.
 2. Thedevice of claim 1, further comprising a conductive via that electricallyconnects the interconnection metal layer to the first electrode or thesecond electrode and wherein the portion of the interconnection metallayer extends onto the insulation layer adjacent a location where theinterconnection layer is disposed on and contacts the conductive via. 3.The device of claim 2, wherein the conductive via passes through theinsulation layer and the piezoelectric layer to contact the firstelectrode.
 4. The device of claim 3, wherein the capacitor electrodeoverlaps a portion of the second electrode.
 5. The device of claim 2,wherein the conductive via extends into and contacts a first portion ofthe second conductive layer that is electrically isolated from a secondportion of the second conductive layer that is electrically connected tothe first electrode and wherein the capacitor electrode overlaps thesecond portion of the second conductive layer.
 6. The device of claim 2:wherein the piezoelectric layer comprises a first portion included in afirst acoustic resonator and a second portion included in a secondacoustic resonator; wherein the first electrode overlaps the first andsecond portions of the piezoelectric layer; and wherein the secondelectrode comprises an electrode overlapping the first portion of thepiezoelectric layer and an electrode overlapping the second portion ofthe piezoelectric layer and the capacitor electrode.
 7. The device ofclaim 6, wherein the capacitor is coupled between an input of the firstacoustic resonator and an output of the second acoustic resonator. 8.The device of claim 1, wherein the capacitor electrode comprises acapacitor electrode of a capacitor coupled between the first and secondelectrodes of the acoustic resonator.
 9. The device of claim 1, whereinthe acoustic resonator comprises a first acoustic resonator and a secondacoustic resonator coupled in series and wherein the capacitor electrodecomprises a capacitor electrode of a capacitor coupled across the seriescombination of the first acoustic resonator and the second acousticresonator.
 10. A device comprising: an acoustic resonator comprising afirst electrode, a second electrode and a piezoelectric region betweenthe first and second electrodes; an insulating layer on the secondelectrode; and an interconnection metal layer on the acoustic resonator,connected by a via to the first electrode or the second electrode andhaving a portion extending onto the insulation layer adjacent the viathat serves as a capacitor electrode.
 11. The device of claim 10,wherein the first electrode is formed from a first conductive layer,wherein the second electrode is formed from second conductive layer,wherein the via connects the interconnection metal layer to the firstconductive layer and wherein the capacitor electrode overlaps a portionof the second conductive layer.
 12. The device of claim 10, wherein thefirst electrode is formed from a first conductive layer, wherein thesecond electrode is formed from second conductive layer, wherein the viaconnects the interconnection metal layer to a portion of the secondconductive layer electrically connected to the first electrode andwherein the capacitor electrode overlaps the portion of the secondconductive layer electrically connected to the first electrode.
 13. Thedevice of claim 10, wherein the piezoelectric region is formed from apiezoelectric layer and wherein the via passes through the piezoelectriclayer.
 14. A method comprising: forming a piezoelectric layer on asubstrate; forming a first conductive layer on a first side of thepiezoelectric layer; patterning the first conductive layer to form afirst electrode for an acoustic resonator; forming a second conductivelayer on a second side of the piezoelectric layer; patterning the secondconductive layer to form a second electrode of the acoustic resonator;forming an insulating layer on the second conductive layer; and formingan interconnection metal layer electrically connected to the secondelectrode layer or the first electrode layer and having a portionextending onto the insulating layer and overlapping a portion of thesecond conductive layer to provide a capacitor electrode of a capacitorcoupled to the first electrode and/or the second electrode.
 15. Themethod of claim 14, wherein forming the interconnection metal layer ispreceded by forming a conductive via electrically connected to the firstelectrode or the second electrode, wherein forming the interconnectionmetal layer comprises forming the interconnection layer on theconductive via, and wherein the portion of the interconnection metallayer extends onto the insulation layer adjacent a location where theinterconnection layer contacts the conductive via.
 16. The method ofclaim 15, wherein forming the conductive via comprises forming aconductive via that passes through the insulation layer and thepiezoelectric layer to contact the first electrode.
 17. The method ofclaim 16, wherein the capacitor electrode overlaps a portion of thesecond electrode.
 18. The method of claim 15, wherein the conductive viaextends into and contacts a first portion of the second conductive layerthat is electrically isolated from a second portion of the secondconductive layer that is electrically connected to the first electrodeand wherein the capacitor electrode overlaps the second portion of thesecond conductive layer.
 19. The method of claim 15: wherein thepiezoelectric layer comprises a first portion included in a firstacoustic resonator and a second portion included in a second acousticresonator; wherein the first electrode overlaps the first and secondportions of the piezoelectric layer; and wherein the second electrodecomprises an electrode overlapping the first portion of thepiezoelectric layer and an electrode overlapping the second portion ofthe piezoelectric layer and the capacitor electrode.
 20. The method ofclaim 19, wherein the capacitor is coupled between an input of the firstacoustic resonator and an output of the second acoustic resonator. 21.The method of claim 14, wherein the capacitor is coupled between thefirst and second electrodes of the acoustic resonator.
 22. The method ofclaim 14, wherein the acoustic resonator comprises a first acousticresonator and a second acoustic resonator coupled in series and whereinthe capacitor electrode comprises a capacitor electrode of a capacitorcoupled across the series combination of the first acoustic resonatorand the second acoustic resonator.